Battery tester with high precision

ABSTRACT

The present invention discloses a battery tester having high precision, which has a casing having an input device and two detecting wires, a microprocessor, a variable loading unit and a battery power status detecting unit. The microprocessor builds a strategic decision process therein to determine a proper resistance of a load for a battery according to the battery capacity, initial voltage and detection requirements having 1/N CCA and loading time. When the resistance of the load is determined, the microprocessor adjusts a resistance of the variable loading unit equal to the resistance of the load for the battery. Therefore, the battery tester does not use the load with the fixed resistance to detect batteries with different capacities and has accurate detecting results.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of a battery tester, and more particularly to a battery tester with high precision.

2. Description of Related Art

There are many types of the rechargeable battery with different capacities on the market. The battery tester is used to detect the residual capacity of the rechargeable battery to determine the health of the rechargeable battery. However, the conventional battery tester uses only one method to detect different rechargeable batteries and inaccurate testing result will likely occur.

In general, the conventional battery tester uses ½Cold Cranking Amps (hereinafter CCA) testing method to detect the health of the rechargeable battery, the method having steps of: (a) adding a load to the two electrodes of the battery to discharge the battery by loading the amperes of ½CCA for 15 seconds; and (b) determining the health of the battery according to the discharging diagram.

In the conventional testing method implemented by the battery tester, the resistance of the load and the duration of adding load to the battery are fixed. Therefore, when the battery tester respectively detects rechargeable batteries with different capacities, figures of the discharging diagrams are not precise. The testing precision of the conventional battery tester is not ideal for all rechargeable batteries.

To overcome the shortcomings, the present invention provides a battery tester with high precision to mitigate or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

Based on the foregoing drawbacks of the conventional battery tester, the main objective of the present invention is to provide a battery tester with high precision.

The battery tester has a casing having an input device and two detecting wires, a microprocessor, a variable loading unit and a battery power status detecting unit. The microprocessor builds a strategic decision process therein to determine a proper resistance of a load for a battery according to the battery capacity, the battery voltage and detection requirements having 1/N CCA and a loading time. When the resistance of the load is determined, the microprocessor adjusts a resistance of the variable loading unit to be equal to the resistance of the load for the battery. Therefore, the battery tester does not use the load with a fixed resistance to detect batteries with different capacities and has accurate detecting results.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a battery tester in accordance with the present invention;

FIG. 2 is a functional block diagram of a first embodiment of a battery tester in accordance with the present invention;

FIG. 3 is a flow chart of a strategic decision process in testing mode implemented in FIG. 1;

FIG. 4 is a circuit diagram of a first embodiment of a variable load unit of the battery tester in accordance with the present invention;

FIG. 5A is a circuit diagram of a first embodiment of a variable load unit of the battery tester in accordance with the present invention;

FIG. 5B is a circuit diagram of a second embodiment of a variable load unit of the battery tester in accordance with the present invention;

FIG. 5C is a circuit diagram of a third embodiment of a variable load unit of the battery tester in accordance with the present invention;

FIG. 6 is a flow chart of a strategic decision process in a first detecting mode implemented in FIGS. 5A, 5B and 5C in accordance with the present invention;

FIG. 7 is a testing diagram of the battery tester in accordance with the present invention; and

FIG. 8 is a flow chart of a detecting process in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1 and 2, a first embodiment of a battery tester with high precision in accordance with the present invention has a casing 10, a microprocessor 20, a variable loading unit 21 and a battery power status detecting unit 22.

The casing 10 has an input device 11 and two detecting wires 12. A user uses the input device 11 to select a specific battery capacity. The detecting wires 12 are respectively and electronically connected to two electrodes 31 of the battery 30. In the first embodiment, the two detecting wires 12 respectively clip to the two electrodes 31 of the battery 30. In addition, the casing 10 further has a display 13, a computer connector 14 and an alarm 15. The computer connector 14 is used to connect to an external electronic device such as a computer or mobile phone. The microprocessor 20 builds a strategic decision process and a detecting process therein.

The variable load unit 21 is electronically connected to the microprocessor 20 and the electrodes 31 of the battery 30 to detect voltage and current changes of the battery 30 and then responds with the voltage and current values to the microprocessor 20.

The battery power status detecting unit 22 is connected between the detecting wires 12 and the microprocessor 20 to detect the battery voltage value and/or current value. Further, the battery power status detecting unit 22 may be built-in the microprocessor 20.

With further reference to FIG. 3, the strategic decision process has the following steps of:

(a) obtaining battery capacity (CCA_(B)) from the input device 11, a battery voltage (V_(B)) of a present battery from the battery power status unit 22, and the detection requirements having 1/N CCA and a loading time from the input device 11 (S10);

(b) calculating an equation of loading resistance with the battery capacity, the initial voltage and the detection requirements to obtain a proper loading resistance for the present battery 30 (S11), wherein the equation is

$\frac{V_{B}}{{CCA}_{B} \times \frac{1}{N}},$

and

(c) executing a detecting process to obtain a detecting curve (S12).

With reference to FIG. 4, the variable loading unit 21 has a variable resistor 21 a and a switch 211. The variable resistor 21 a is electronically connected to the detecting wires 12. The variable resistor 21 a is electronically connected to the microprocessor 20. The switch 211 is electronically connected between one of the detecting wire 12 and the corresponding end of the variable resistor 21 a. The microprocessor 20 adjusts resistance of the variable resistor 21 a. The microprocessor 20 further controls the switch 211 to be turned on or off.

For example, if the user detects the health of the present battery 30 with 12 V/1000 CCA, the user may select ½ CCA to detect the battery 30 by the input device 11. Therefore, the microprocessor 20 of the battery tester obtains detection requirements: CCA_(B)=100 CCA, V_(B)=12V, 1/N CCA=½ CCA, so a proper loading resistance is calculated by the equation of loading resistance and the resistance will be 0.024 ohm. The microprocessor 20 controls the variable resistor 21 a to adjust the resistance of the variable resistor 21 a to be 0.024 ohm. When the detecting wires 12 are used to clip to the electrodes 31 of the battery 30, the variable resistor 21 a with 0.024 ohm is added to the battery 30.

In another example, if the user detects the health of the present battery 30 with 12 V/900 CCA, the user may select ⅓ CCA to detect the battery 30 by the input device 11. Therefore, the microprocessor 20 of the battery tester obtains detection requirements: CCA_(B)=900 CCA, V_(B)=12V, 1/N CCA=⅓ CCA, so a proper loading resistance is calculated by the equation of loading resistance and the resistance will be 0.04 ohm. The microprocessor 20 controls the variable resistor 21 a to adjust the resistance of the variable resistor to be 0.04 ohm. When the detecting wires 12 clips to the electrodes of the battery 30, the variable resistor with 0.04 ohm is added to the battery 30.

Based on the above two examples, the resistance of the variable resistor can be changed according to the different capacities of the batteries.

With further reference to FIG. 5A, another embodiment of the variable loading unit 21 has multiple resistors 21 b and switching elements 21 c. First ends of the resistors 21 b are electronically connected to the detecting wires 12 and second ends of the resistors 21 b are respectively and electronically connected to the other detecting wire 12 through the corresponding switching elements 21 c. The switching elements 21 c are electronically connected to the microprocessor 20. The microprocessor 20 drives each switching element 21 c to be turned on or turned off to determine which one resistor 21 b is connected to the two electrodes 31 of the battery 30, or which resistors 21 b are electronically and parallelly connected to the two electrodes 31 of the battery 30. When a proper loading resistance is determined by the microprocessor 20, the microprocessor 20 drives one or more switching elements 21 c to be turned on according to the loading resistance. If two or more switching elements 21 c are driven to be turned on at the same time, the resistance of the variable loading unit is smaller than that of one of the resistors 21 b.

With reference to FIG. 5C, another embodiment of the variable loading unit has a programmable variable resistor 21 e and a switch 211. The programmable variable resistor 21 e is electronically connected to the detecting wires 12. A controlling end of the program variable resistor 21 e is connected to the microprocessor 20. The microprocessor 20 directly adjusts the resistance of the programmable variable resistor 21 e and drives the switch 211 to be turned on or off to determine whether the programmable variable resistor 21 e is connected to the battery 30 or not. In addition, the microprocessor 20 is connected to the controlling end of the programmable variable resistor 21 e through a buffer 21 f. For example, if the resistors 21 b have the same resistance as in FIG. 5A, and the resistance is 0.08 ohm, one battery with 12V/750 CCA is detected by the battery tester as shown in FIG. 5A. The user uses the input device 11 to select the ½CCA and 15 sec loading time to enter the testing process.

Since the resistors 21 b have the same resistance, the loading of the battery is 0.08 ohm when the microprocessor 20 drives one of the switches 21 c to be turned on. The microprocessor 20 has a power status detecting unit 22 to detect a present current value of the battery 30 with 0.08 ohm. When the current value is equal to 100 A, the microprocessor 20 calculates a proper loading resistance and the calculating process has the following steps of:

(a) calculating the numbers of the resistors with 0.08 ohm; wherein [750*(½)]/100=3.75; and

(b) calculating a total detecting power by ½ CCA and 15 sec, wherein the total detecting power is [750*(½)]*15=5625(A-sec).

Since the microprocessor 20 just selects 3 resistors 21 b to parallelly connect to the battery 30, the initial detection requirements input by the user are changed. A new loading time is changed to 18.75 sec as calculated by an equation: 5625/300=18.75 sec.

In this example, the microprocessor 20 turns on 3 switches 21 c, and the 3 resistors 21 b are electronically and parallelly connected to the battery 30 for 18.75 sec.

With further reference to FIG. 5B, another embodiment of the variable loading unit has multiple resistors 21 b connected in serial and a 1 to X multiplexer 21 d having one common terminal COM and X switching terminals S₁ to S_(x). X is the number of the resistors 21 b. One end A of the series of the resistors is connected to one detecting wire 12 and the other detecting wire 12 is connected to the common terminal COM of the multiplexer 21 d. The switching terminals S₁ to S_(x) of the multiplexer 21 d are respectively connected to serial nodes of the series of the resistors 21 b and the other end B of the series of the resistors 21 b. The microprocessor 20 drives the common terminal COM to connect to one of the switching terminals S₁ to S_(X) to determine a resistance of the variable loading unit.

For example, the resistors 21 b have the same resistance (0.08 ohm) and a battery with 12V/1000 CCA is detected. The user selects ½ CCA and 15 sec loading time to detect the health of the battery 30.

Since the variable loading unit has multiple resistors 21 b, one resistor 21 b is first connected to the battery 30 by driving the multiplexer 21 d and detects whether a present current value achieves 12/0.08=150 A. If the current value achieves 150 A, the microprocessor 20 further calculates a proper loading for the present battery 30. The calculating process has the following steps of:

(a) 1000/2*15=7500(A-sec); and

(b) 75000/150=50(sec).

When the microprocessor 20 executes the loading process, the microprocessor 20 drives multiplexer 21 d and the common terminal COM is connected to a first switching terminal S₁. One resistor 21 b is selected to connect to the battery 30 through the detecting wires 12. In addition, the initial loading time (15 sec) is changed to 50 sec as a new loading time.

For another example, to detect another battery 30 with 12V/100 CCA, the microprocessor 20 drives the multiplexer 21 d and selects 3 resistors 21 b to connect to the battery 30 to detect the present current value (12V/0.24=50 A). According to the present current value, the microprocessor 20 calculates a proper loading resistance. The calculating method has the following steps of:

(a) 100/2*15=750(A); and

(b) 750/50=15 (sec), wherein the final loading time is equal to the initial loading time selected by the user: the loading time is not changed.

When the microprocessor 20 executes the loading process, the microprocessor 20 drives multiplexer 21 d, and the common terminal COM is connected to a third switching terminal S3. The series of the three resistors 21 b is selected to connect to the battery 30 through the detecting wires 12 to detect aging of the battery 30.

Based on the foregoing description of the two embodiments in FIGS. 5A and 5C, the strategic decision process of microprocessor 20 has the following steps of:

(a) obtaining the capacity (CCA_(B)), voltage (V_(B)) and input detecting requirements from the input devices (S20);

(b) adding at least one resistor 21 b to connect to the battery 30 by driving one of the switches 21 c or the multiplexer 21 d to detect a proper current value (S21);

(c) calculating the proper loading resistance according to the proper current value to adjust the resistance of the variable loading unit (S22), wherein an equation

of calculating resistance is

$\frac{{CCA}_{B} \times \frac{1}{N}}{I_{B}};$

(d) calculating the equation of calculating the total detecting time with the initial testing information including 1/N CCA and loading time (T_(LOAD)) (S23), wherein the equation of calculating the total detecting time is (CCA_(B)×1/N)×T_(LOAD);

(e) changing the initial loading time according to the numbers of the resistors selected by microprocessor (S24); and

(f) executing the detecting process to obtain a detecting curve (S25).

Based on the foregoing description, the variable loading unit 21 has multiple resistors 21 b but the microprocessor 20 executes the strategic decision process to adjust the numbers of the resistors 21 b and changes the initial loading time selected by the user. Therefore, the microprocessor 20 still obtains accuracy, detecting curves for the battery 30 with different capacities.

With reference to FIGS. 1, 7 and 8, the detecting curve obtained by the microprocessor 20 and the flow chart of the detecting process are shown. In detecting process, the battery 30 is first charged to full capacity and just removed from a charger. The variable loading unit 21 is then connected to the battery 30. The microprocessor 20 detects a discharging power of the battery 30 through the variable loading unit 21 and monitors whether a discharging power of the battery 30 achieves a present power vale (V_(e2)). When the discharging power achieves the present power value, the switches 21C are removed from the battery so the variable loading unit 21 is disconnected from the battery (S40). Therefore, the battery 30 has no surface charge voltage. Then, the variable loading unit 21 is alternatively connected to the battery 30 to detect multiple voltage values and current values of the battery 30 (S41). Finally, the detecting curve is completed by the voltage values and/or current values and the microprocessor determines the health of the battery according to the detecting curve (S42).

Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A battery tester with high precision, comprising: a casing having: an input device providing different options of battery capacities and detection requirements; and two detecting wires adapted to selectively connect to two electrodes of a battery; a microprocessor building a strategic decision process therein; a variable loading unit electronically connected to the microprocessor and connected to the detecting wires; and a battery power status detecting unit electronically connected to the microprocessor to detect a voltage and current of the battery and reporting the voltage and current to the microprocessor.
 2. The battery tester as claimed in claim 1, wherein the variable loading unit is a variable resistor having: two ends respectively connected to the detecting wires; and one controlling end electronically connected to the microprocessor so that the microprocessor adjusts the resistance of the variable resistor.
 3. The battery tester as claimed in claim 2, wherein the strategic decision process has steps of: (a) obtaining battery capacity (CCA_(B)) and a battery voltage (V_(B)) of a present battery and reading the detection requirements having 1/N CCA and loading time; (b) calculating an equation of loading resistance with the battery capacity, the initial voltage and the detection requirements to obtain a proper loading resistance for the battery; wherein the equation is $\frac{V_{B}}{{CCA}_{B} \times \frac{1}{N}};$ and (c) executing a detecting process to obtain a detecting curve.
 4. The battery tester as claimed in claim 1, wherein the variable loading unit has multiple resistors and multiple switches electronically connected to the microprocessor, wherein one end of each resistor is connected to one of the detecting wires, and the other end of the resistors are respectively connected to the other detecting wire through the switches.
 5. The battery tester as claimed in claim 1, wherein the variable loading unit has: multiple resistors connected in serial to be a series of the resistors, wherein one end of the series of the resistors is connected to one of the detecting wire; and a multiplexer having: a common terminal connected to the other detecting wire; multiple switching terminals respectively connected to serial nodes of the series of the resistors and the other end of the series of the resistors; and a controlling terminal electronically connected to the microprocessor, so that the microprocessor drives the multiplexer to determine which one of the switching terminals is connected to the common terminal.
 6. The battery tester as claimed in claim 1, wherein the variable loading unit has: a programmable variable resistor having a controlling end electronically connected to the microprocessor; and a switch connected between the programmable variable resistor and the detecting wire, and electronically connected to the microprocessor.
 7. The battery tester as claimed in claim 1, wherein the variable loading unit has: a programmable variable resistor having: two ends respectively connected to the detecting wires; and a controlling end electronically connected to the microprocessor; a buffer electronically connected between the microprocessor and controlling end of the programmable variable resistor; and a switch connected between one end of the programmable variable resistor and the detecting wire, and electronically connected to the microprocessor.
 8. The battery tester as claimed in claim 4, wherein the strategic decision process has steps of: (a) obtaining the capacity (CCA_(B)), the voltage (V_(B)) and the detecting requirements having 1/N CCA and loading time; (b) adding at least one resistor to connect to the battery by driving one of the switches to detect a proper current value; (c) calculating the resistance of the variable loading unit according to the current value, wherein an equation of calculating resistance is $\frac{{CCA}_{B} \times \frac{1}{N}}{I_{B}};$ (d) calculating the equation of calculating the total detecting time with initial testing information including 1/N CCA and loading time, wherein the equation of calculating the total detecting time is (CCA_(B)×1/N)×T_(LOAD); (e) changing the initial loading time according to the numbers of the resistors selected by microprocessor; and (f) executing the detecting process to obtain a detecting curve.
 9. The battery tester as claimed in claim 5, wherein the strategic decision process has steps of: (a) obtaining the capacity (CCA_(B)), the voltage (V_(B)) and the detecting requirements having 1/N CCA and loading time; (b) adding at least one resistor to connect to the battery by driving the multiplexer to connect the common terminal to one of the switching terminals to detect a proper current value; (c) calculating the resistance of the variable loading unit according to the current value, wherein an equation of calculating resistance is $\frac{{CCA}_{B} \times \frac{1}{N}}{I_{B}};$ (d) calculating the equation of calculating the total detecting time with the initial testing information including 1/N CCA and loading time, wherein the equation of calculating the total detecting time is (CCA_(B)×1/N)×T_(LOAD); (e) changing the initial loading time according to the numbers of the resistors selected by microprocessor; and (f) executing the detecting process to obtain a detecting curve.
 10. The battery tester as claimed in claim 3, wherein the detecting process has steps of: (a) charging the battery to full capacity and then just removed from a charger; (b) connecting the variable loading unit to discharge the battery and monitoring the discharging power status; (c) disconnecting the variable loading unit from the battery until the battery discharges to a present discharging power value; (d) alternatively connecting the variable loading unit to the battery to detect multiple voltage values and current values of the battery; and (e) completing the detecting curve by the voltage values and current values.
 11. The battery tester as claimed in claim 8, wherein the detecting process has steps of: (a) charging the battery to full capacity and then just removed from a charger; (b) connecting the variable loading unit to discharge the battery and monitoring the discharging power status; (c) disconnecting the variable loading unit from the battery until the battery discharges to a present discharging power value; (d) alternatively connecting the variable loading unit to the battery to detect multiple voltage values and current values of the battery; and (e) completing the detecting curve by the voltage values and current values.
 12. The battery tester as claimed in claim 9, wherein the detecting process has steps of: (a) charging the battery to full capacity and then just removed from a charger; (b) connecting the variable loading unit to discharge the battery and monitoring the discharging power status; (c) disconnecting the variable loading unit from the battery until the battery discharges to a present discharging power value; (d) alternatively connecting the variable loading unit to the battery to detect multiple voltage values and current values of the battery; and (e) completing the detecting curve by the voltage values and current values.
 13. The battery tester as claimed in claim 1, wherein the casing further comprises a display, a computer connector and an alarm. 